High-frequency signaling system



E. F. W. ALEXANDERSON HIGH FREQUENCY SIGNALING SYSTEM Filed Aug. 29 1921 Inventor-I .Ern st F. W. Alexn arson,

, H is Attor n ey.

Patented July 8, 192%.

NE' 'T ERNST F. W. AL

or SCHENECTADY, unw Yank, ASSIGNOR 'ro GENERAL nanc'rmc coraranv, a coaronarron or Y0 a HIGH-FREQUENCY SIGNALING SYS.

Application filed August 29, 1921. Serial No. 496,229.

a simple and efficient method of and apparatus for transmitting telegraphic signals by means of high frequency alternating currents.

The usual telegraphic code employed for transmitting messages by means of electric currents is made up of two principal characters differing from one another only in their time interval, a dot representing a time interval about half. that of a dash. It is evident, therefore, that by reason of this fact a longer time is required for the transmis sion ofa message than would be the case if all characters were represented by the smaller time interval required for the transmission of a dot.

A more specific object of my invention is to provide a method of and a paratus for signaling which will permit 0 a reduction of the time required for transmission of a message by allowing for the same time interval for both dots and dashes. To accomplish this result I differentiate between dotsand dashes by transmittiing waves of difierent fre uency.

In one em odiment of my invention 1 provide two sources of high frequency current, such for example, as two high frequency alternators of different frequency and connect both of these sources to the antenna. I also provide means for practically short circuiting at will either one of these sources so that the other source alone will supply energy to the antenna. In; addition I provide controlling means which is arranged in such a way that when one of the sources is short circuited the tuning of the antenna is changed so that the antenna becomes resonant for the frequency of the other source which is supplying energy to the antenna at that instant. v

lhenovel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation will best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 shows diagrammatically the application of my' invention to a radio transmitting system; Fig. 2 shows a receiving system for receiving and recording the message transmitted; and Fig. 3 shows a modification in the method of transmitting the message.

As shown in Fig. 1 of the drawing, I provide two sources of high ferquency current 1 and 2 which are connected by means of transformers 3 and 4 to a transmitting circuit which in the present case is indicated as an antenna 5, altho it may equally well be a wire line if d ired. In shunt to the secondary of the transformer 8, I provide a magnetic amplifier having high frequency windings 6 and the usual series condensers 7 and S. Current for saturating. the core of the magnetic amplifier is supplied to the saturation winding 9 from a source 10 of direct current by means of a key 11. The current supplied to the antenna 5 by the connections indicated will vary in inverse proportion to the amount of current supplied to the saturation winding 9. When no current is sup-plied to this saturation/ winding full current from the source 1 will be supplied to the antenna 5. When a current is supplied to the saturation. winding 9, the impedance of the high frequency windings 6 of the magnetic amplifier will decrease and these windings will act more or less as a short circuit on the secondary of transformer 3, depending upon the value of the saturation current, and hence, the

amount of current supplied to the antenna saturation windings and both sources of current are practically short circuited so that substantially no radiation takes place. When the key is raised so that it makes contact only with segment 16, the current in saturation winding 15 is interrupted thereby removing the short circuit from source 2 and permitting radiation from that source to take place. When the key is depressed so that it makes contact only with segment 17, the current in saturation winding 9 is interrupted thereby removing the short circuit from source 1 and permitting radiation from that source'to take place.

When source 1 is radiating, the tuning of the antenna will be determined chiefl' by the loading coil 18, the inductance o the transformer 3 and the inductance of the high frequency windings 12 of the magnetic amplifier associated with source 2, the inductance of these windings at this time being small in comparison with the inductance of the transformer 4. In order to change the tuning of the antenna when source 2 is radiating, the high frequency windings of the amplifier associated with source 1 may be connected to an intermediate point 19 in the loading coil 18. The tuning of the antenna will then be determined by the portion of the loading coil above point 19, the inductance of windings 6 and the inductance of transformer 4. By proper adjustments, the two different tunings of the antenna obtained in this way may be made to correspond to the two frequencies sup-plied by the sources 1 and 2.

It will of course be understood that the showing ofthe key 11 is purely diagrammatic and that any suitable switching means desired may be employed to effect the transmission of the desired wave. In case automatic transmission is desired, this may be effected by the use of a perforated tape 20, as indicated in Fig. 3, having two rows of perforations thereon, one ofthese rows representing the dots and the other row representing the dashes of the message. The tape may, by any suitable means, be caused to pass between two pairs of contacts 21 and 22. The circuits of the saturationwindings 9 and 15 which are supplied with current from the source 10 may be closed through the contacts 21 and 22 whenever a perforation in the tape passes under these contacts. I

At the receiving station the current transmit-ted may be received upon an antenna 23 and supplied t the usual tuned receiving circuits 24 and 25 which are tuned respectively to the two frequencies of sources 1 and 2 and which are associatedwith detectors 26 and 27. In the plate circuits of these detectors may be inserted windings 28 and 29 of a relay having a movable armature 30, the movement of which is controlled two sources of high frequenc by either of the two windings. The armaergy is radiated from source 2 the detector 27 will operate and coil 29 will attract the armature 30, making indications 33 representing dashes on the tape.

In addition to shortening the time required to transmit a message by making the time interval for a dash equal .to the time interval for a dot, a further shortening of the time required for transmission may be efiected by reducing the time interval between the successive characters of a letter. In the illustration I have indicated an interval between successive characters which is small in comparison with the time required to transmit a dot. This interval is so small that the armature 30 does not have time to return to its normal central position between successive characters of a letter. Na difiiculty will be experienced in reading the message record-ed however, as

the number of successive dots or dashes can readily be observed from the small waves in the record line or from the space interval occupied on the tape by the'characters of a letter.

While I have shown diagrammatically and described only one embodiment of my invention, namely, its application to a radio signaling system, it will be apparent that it may equally well be employed for transmitting signals overwire lines and that many modifications in the circuit arrangement and apparatus used may be made w1thout departing from the scope of my invention as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. The combination in a high frequency signaling system of a transmitting circuit, current of different frequencies connecte to said circuit, connections for practically suppressing at will the current delivered from either of said sources without disconnecting the source from the circuit and means for changing the tuning of the transmitting circuit at the same time that one of the suppressing connections is made or removed. 2. The combination in a high frequency signaling system of a transmitting circuit, twov sources of high frequency current of different frequencies connected to said circuit by means of transformers, connections for practically suppressing at will the potential of the secondary of either of said transformers without disconnecting the primary and means for changing the tuning of the transmitting circuit at the same time that one of the suppressing connections is made or removed.

3. The combination in a high frequency signaling system of a transmitting circuit, two sources of high frequency current of different frequencies connected to said circuit by means of transformers, an impedance in said transmitting circuit, and connections for practically suppressing at will the potential of the secondary of either of said transformers without disconnecting the primary, the connections for suppressing one of said secondaries including a portion of said impedance in the transmitting circuit.

'4. The combination in a high frequency signaling system of a transmitting circuit, two sources of high frequency current of different frequencies connected to said circuit by means of transformers, and means associated with each transformer secondary for substantially short circuiting the-same and at the same time changing the tuning of the transmitting circuit.

5. The combination in a high frequency signaling system of a transmitting circuit, two sources of high frequency current of different frequencies connected to said circuit by means of transformers, and magnetic amplifiers associated with each transformer secondary for substantially short circuiting the same and at the same time changing the tuning of the transmitting circuit.

6. The combination in a high frequency signaling system of a transmitting circuit,

two sources of high frequency current of different frequencies connected to said circuit by means of transformers the secondaries of which are connected in series in the transmitting circuit, and means associated with each transformer secondary for substantially short circuiting the same and at the same time changing the tuning of the transmitting circuit.

7. The combination in a high frequency signaling system of a transmitting circuit, two sources of high frequenc current of different frequencies connecte to said circuit by means of transformers the secondaries of which are connected in series in the transmitting circuit, and magnetic amplifiersassociated with each transformer secondary for substantially short circuiting the same and at the same time changing the tuning of the transmitting circuit.

8. The combination in a high frequency signaling system of a transmitting circuit, two sources of high frequency current of different frequencies connected to said circui-t by means of transformers the secondaries of which are connected in series in the transmitting circuit, an impedance connected in series in the transmitting circuit, a magnetic amplifier connected in shunt.

to the secondary of one ti ansformer and a second magnet1c amplifier connected in shunt to the secondary of the second transformer and said impedance.

In witness whereof, I have hereunto set my hand this 26th day of August, 1921.

ERNSTVF. w. ALEXANDERSON. 

